A hand has surface data derived from wrinkles on the hand, which is called a palmar pattern or lines on the palm in palmistry. Further, a finger joint also has finger surface data derived from bending and stretching the finger. The following technology is exemplified as a technology of acquiring surface data of the hand.
There is a technology which is targeted mainly at the finger and uses two images, i.e., an image captured by utilizing transmitted beam and an image captured by utilizing reflected light. A larger quantity of surface data is taken in the image captured by utilizing the reflected light than in the image capture by utilizing the transmitted light. Such being the case, the surface data of an object can be specified by taking a difference between the two images.
Further, an object having unevenness (concave/convex portions) is illuminated with light beams in different directions, with the result that different shadows are formed. A target object is imaged by making use of this phenomenon in a manner that utilizes a plurality of illuminations which is different in any one or plural elements among an intensity of the illumination light, a direction of the illumination light, a wavelength of the illumination light, an imaging direction and a period of imaging time. The surface data of the target object can be specified by analyzing a difference between these captured images.    [Patent document 1] Japanese Patent Application Laid-Open Publication No. 2004-255212    [Patent document 2] Japanese Patent Application Laid-Open Publication No. 2006-244234    [Patent document 3] Japanese Patent Application Laid-Open Publication No. 2004-185276    [Patent document 4] Japanese Patent Application Laid-Open Publication No. H04-277874    [Patent document 5] Japanese Patent Application Laid-Open Publication No. 2003-50993    [Patent document 6] Japanese Patent Application Laid-Open Publication No. 2006-99700